基于GlobeLand30的城市生态用地时空变化特征——以北京市为例

在城市高速增长而土地资源有限的背景下，北京市探索了城市总体规划统领的生态保护与建设有效途径，探究其生态用地时空变化特征，能够为生态用地与建设用地同步规划和协调布局提供参考。本文基于北京市2000年、2010年和2020年的GlobeLand30土地覆盖数据，分析了2000-2020年生态用地与建设用地、农用地的相互转化，揭示了各类用地变化强度在不同距离及方位的空间分布特征，应用景观格局指数刻画了空间形态变化；通过景观扩张/收缩指数LESI判定生态用地空间形态变化模式；通过高斯两步移动搜索法2SFCA计算建设用地与生态用地的可达性。结果表明：（1）生态用地面积占比一直为13%~15%，但不同距离和方位的空间分布发生显著变化，生态条件较好区域受城市增长负面影响较大，生态条件相对薄弱区域的生态建设在城市增长中加强。（2）生态用地的空间形态变化不大，但空间分布趋于分散；生态用地增加以新生模式和扩展模式为主，减少则从消亡模式为主转向分裂模式和收缩模式为主。（3）建设用地与生态用地的可达性整体偏低，2000-2010年新增建设用地可达性的低等级占比高于既有建设用地，可达性高值区零散分布在中心区域；2010-2020年新增建设用地可达性的较高等级占比高于既有建设用地，可达性较高区域的空间分布更加均匀。

Spatial and temporal change characteristics of ecological land in Beijing based on GlobeLand30

In the background of rapid urban development and the constraints of available land resources, Beijing has explored effective ways to coordinate ecological protection and urban development under the framework of the city''s master plan. To provide a reference for the synchronized planning and coordinated layout of ecological land and construction land, it is necessary to analyze the spatial and temporal characteristics of ecological land change in the process. Based on the GlobeLand30 land cover data of Beijing in 2000, 2010 and 2020, this paper analyzed the interconversion of ecological land, construction land and agricultural land from 2000 to 2020, revealed the spatial distribution characteristics of land change intensity of various types of land use at different distances and orientations. Moreover, it further depicted the spatial and morphological pattern of ecological land changes by using Landscape Pattern Index and Landscape Expansion/Shrink Index (LESI). In addition, the accessibility to ecological land was calculated by Gaussian based 2-step floating catchment area (2SFCA) method. The results show that: (1) The proportion of ecological land area has been maintained at 13%-15% from 2000 to 2020, but the spatial distribution presented at different distances and orientations has changed significantly, with areas with better ecological conditions being more negatively affected by urban growth and areas with relatively weak ecological conditions being strengthened in the ecological construction of urban growth; (2) The spatial distribution of ecological land tends to be dispersed, even when the total area remains stable. The increase in ecological land is dominated by the outlying and edge-expansion growth patterns, while the decrease shifts from extinction pattern to fragmentation and contraction patterns; (3) The accessibility of construction land and ecological land is generally low. From 2000 to 2010, the accessibility of new construction land has a higher percentage of low grade than that of existing construction land, and the high accessibility areas are scattered in central areas; from 2010 to 2020, the accessibility of new construction land has a higher percentage of high grade than that of existing construction land, and the spatial distribution of higher accessibility areas is more uniform.